This invention relates to a process for preparing a piece having spiders bent in the axial direction of the piece and more particularly, to a process for preparing a pole piece for the rotor of a vehicle AC generator.
As more clearly shown in FIG. 9, a pole piece for the rotor of an AC generator generally comprises a base having a plurality of radial spiders formed on the outer periphery and bent in parallel in the axial direction of the base and a center boss formed on one surface of the base. In use, a pair of such pole pieces are disposed with their bosses positioned in face-to-face relationship and the spiders on one pole piece fitted in the valleys defined between the adjacent spiders on the other pole pieces.
The forging and bending systems have been known as the conventional processes for preparing pole pieces of the type referred to hereinabove. The former or forging system comprises the steps of cutting a slug having a predetermined volume off from a round metal bar of an indefinite length, heading the slug, extruding the headed slug to provide a semiprocessed product having a base and a plurality of bent radial pieces on the periphery of the base and trimming the thus obtained semiprocessed product to provide a complete pole piece. Although this system is a high yield rate process, the system has the disadvantage that the system requires a high capacity press which provides a high processing force and necessiates a large scale facility.
And the latter or bending system comprises the steps of stamping a blank having a plurality of radially and outwardly extending spiders out of a metal plate material, bending the spiders at right angles to the plane of the blank and attaching a boss to one surface of the blank. However, since the blank stamped by this system has the radially and outwardly extending spiders, this system is disadvantageous with respect to consumption of material or this system is a low yield rate and uneconomical process. Nevertheless, the bending system has the advantage that the system can be performed by the use of a low capacity press which provides a low processing force. Thus, the forging and bending pole piece preparing systems have their inherent advantages and disadvantages and in consequence, a process for the purpose which is easily carried out and economical has been long wished for.